Existing laser transmitters for optical communication and ranging applications operate at wavelengths already occupied by the high background noise of the solar spectrum, making reception difficult. For undersea and sea-surface penetrating applications existing systems use dye lasers with material lifetime problems and expensive secondary optical pumping lasers, or xenon chloride excimer lasers with toxic-corrosive gases and 1300.degree. C. lead vapor Raman cells, or frequency doubled solid-state neodymium based lasers operating far from the peak transmission band for blue-ocean seawater, or low peak-power 1500.degree. C. copper vapor lasers. A comparatively simple solid-state high peak-power laser transmitter operating at the minimum solar background and highly blue-ocean penetrating calcium g Fraunhofer line would be an improvement in the state of the art of laser communication and ranging systems. This is particularly true if the laser is efficiently and reliably diode pumped and wavelength matched to a calcium atomic resonance filter also on the calcium g Fraunhofer line.
Thus a need currently exists in the state of the art for an improvement in laser communications and ranging systems 11 using a comparatively simple neodymium solid-state high peak-power laser transmitter operating at selective wavelengths of minimum solar background radiation and maximum seawater transmission.